1. Field of the Invention
The present invention generally relates to a rescue braking system, and more particularly, to a rescue braking system for rescuing trapped elevator passenger by mechanically lifting or applying the brake with a brake release cable.
2. Description of the Background Art
The machine-roomless (MRL) elevator systems were introduced several years ago. MRL elevators use permanent magnets to boost the power of the motor. This reduces the size of the motor so that it is small enough to fit within the elevator hoistway rather than requiring a separate machine room. With the MRL elevator systems, the developers are able to utilize the full height of the building for floor space without having to sacrifice the top floor for a machine room. If a building is subject to height restrictions, an MRL elevator might allow the structure to meet the restriction by reducing the height needed for a new building. What's more, MRL systems allow greater flexibility in locating the elevators without structural considerations.
In the MRL elevator systems, the elevator brake is no longer easily accessible because there is no machine room. In other words, the conventional rescue systems which require accessing the brake in the machine room are no longer applicable. Therefore, rescue of passengers trapped in an MRL elevator system under an emergency circumstance, such as an electricity outage or control system failure, becomes an important issue.
Several elevator rescue systems have been proposed and implemented for rescuing trapped elevator passenger from the MRL elevators. One conventional system involves applying voltage to the motor coils of the brake. Such a system repeatedly energizes and de-energizes the brake coils to alternately release and apply the brake of the elevator car. FIG. 1 shows the speed of the elevator car during the operation of the conventional elevator rescue system, as shown in FIG. 1, when the elevator moves too fast, the elevator rescue system would apply voltage to the motor coils so that the brake is fully open. On the other hand, when the elevator moves too slowly, the rescue system would apply voltage to the motor coils so that the brake was fully off and the elevator car moves freely.
In other words, the brake in the conventional rescue system is always fully on or off, which causes a jerky vibration on the elevator car as the elevator car drifts to the nearest floor door. Such jerky vibration would make the trapped passengers uncomfortable and may cause some injury. Also, such a system is noisy.
Therefore, there is a need in the art for an elevator rescue system to make the elevator car drift smoothly to a desired floor.